Method and apparatus for cleaning a pipe with sonic energy



Jan. 14, 1969 s. E. JACKE 3,421,939

METHOD AND APPARATUS FOR CLEANING A PIPE WITH SONIC ENERGY Filed Dec. 27, 1965 HIGH FREQUENCY GENERATOR V v G 1 FIGQ4 GENERATOR IS a l l6 -H I i g 'L 20 i mrvzm'on. w v STANLEY E. JACKE United States Patent 3,421,939 METHOD AND APPARATUS FOR CLEANING A PIPE WITH SONIC ENERGY Stanley E. Jacke, Ridgefield, Comm, assignor to Branson Instruments, Incorporated, Stamford, Conn, a corporation of Delaware Filed Dec. 27, 1965, Ser. No. 516,483

US. Cl. 134-1 13 Claims Int. Cl. 1308b 3/10 ABSTRACT OF THE DISCLOSURE The inside surface of a liquid-filled pipe is cleaned by using a resonating horn having a bell-shaped frontal portion. The horn is coupled to an electro-acoustic transducer which is immersed in the liquid and operates in the sonic or ultrasonic frequency range for causing cavitation in the liquid. The bell-shaped portion provides radial shock waves, effecting a scrubbing action upon the inside pipe surface at a location opposite the horn.

This invention generally refers to a method and apparatus for cleaning the inside surface of a pipe and more specifically concerns a method and apparatus for cleaning such a surface with sonic energy.

As is well known, the cleaning of the inside of pipes presents considerable problems and has not been accomplished very successfully. Most methods employ liquid rinses, high speed flushes, both either alone or in combination with various mechanical scrubbing implements. Cleaning of contaminated articles by the use of a sonical- 1y cavitated liquid, particularly a solvent, has proven very successful in industrial processes and has found widespread use. Little has been done however, to reduce this process to practice for cleaning the inside of pipes.

The method and apparatus described hereafter provides a relatively simple and convenient arrangement for effecting a highly efiicient cleaning and scrubbing of the inside surface of pipes and similar containers. The present combination of elements is particularly successful when a high degree of cleaness is important, such as is the case in feed lines for missile fuels and other aerospace and chemical applications. Quite obviously, the described method and apparatus may be used also to good advantage in many industrial and chemical installations.

One of the principal objects of this invention is, therefore, the provision of a new and improved method and apparatus for cleaning the inside of pipes and similar containers.

Another important object of this invention is the provision of a method and apparatus for cleaning the inside diameter of pipes by means of sonic energy, using a liquid immersible electro-acoustic transducer.

A further object of this invention is the provision of a method and apparatus for scrubbing the inside of a liquid filled pipe by introducing acoustic energy into the liquid so as to cause cavitation whereby to effect a highly intensive scrubbing of the inside surface of the pipe.

Further and still other objects of this invention will be more clearly apparent by reference to the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic illustration of the apparatus for providing sonic energy in a liquid filled pipe;

FIGURE 2 is an enlarged sectional view of the end portion of the acoustic horn coupled to the electro-acoustic transducer;

FIGURE 3 is a view along lines 3-3 in FIGURE 2, and

3,421,939 Patented Jan. 14, 1969 FIGURE 4 is a vertical view, partly in section, of the typical cleaning arrangement.

Referring now to the figures and FIGURE 1 in particular, there is shown a high frequency generator 12 which provides electrical energy, typically at 20 kilocycles per second, via a cable 14 to an electro-acoustic transducer unit 16. The electro-acoustic transducer unit includes one or more piezoelectric discs for producing mechanical motion in response to the electrical energy applied thereto. The construction of this transducer unit is described also in copending application for US. Letters Patent Ser. No. 384,025, filed on July 13, 1964, by Stanley E. Jacke et al., now Patent No. 3,328,610, dated June 27, 1967, entitled Sonic Wave Generator. It will be apparent that a transducer unit using a magnetostrictive transducer may be substituted without deviating from the principle described.

The transducer unit, in response to the electric energy applied thereto, provides mechanical oscillations in the longitudinal direction and, in order to amplify these oscillations, an acoustic horn 18 is mechanically coupled to the transducer 16. The horn length is selected so as to provide maximum motional excursion at the frontal surface of the horn.

Since the transducer unit is immersed in a liquid during use, the unit is enclosed in a water-tight housing and the horn is sealed relative to the housing by means of an O-ring gasket. This type of scaling is well understood and therefore is not specifically shown in the drawings. Sealing is accomplished most suitably at a nodal point of the horn 18 where the longitudinal motion is substantially zero. The forced air cooling means contained within the transducer unit 16 and shown in the application for Letters Patent supra is deleted since the liquids into which the transducer is normally immersed provide for adequate heat transfer.

For the present application, the horn 18 is provided with a bell-shaped open ended front portion 20, the front wall being made relatively large in diameter and terminating in an annular rim of decreasing cross-section in order to provide cross coupling between the longitudinal and radial modes of oscillation. It has been observed that a horn of this shape, particularly when the barrel portion 22 is filled with a medium having a low acoustic impedance, such as air, vibrates to a substantial degree in its radial mode at the area of the front portion 24. The direction of vibration is indicated by the arrows 26 in FIGURE 1.

FIGURES 2 and 3 show the general shape of the front portion of the horn 18 in an enlarged scale. The vibrations of the horn at the front portion reflect themselves as radial swellings and contractions, as is indicated by the dashed lines in FIGURE 2. The horn itself is made most suitably of good acoustic material, resistant to the attack from the liquids. Titanium is a typically suitable material.

FIGURE 4 illustrates the use of the transduced unit for cleaning pipes. The transducer unit 16 with horn is immersed in a pipe 30 which is filled with a suitable liquid 32. This liquid may be the liquid normally carried by the pipe, or it may be a special cleaning solvent, such as trichlorotrifiuoroethane or any other suitable liquid cleaning medium.

The transducer unit, in the preferred mode of operation, is inserted into the pipe so that air is trapped in the barrel portion 22 of the horn and occupies a portion of this space. When activating the generator 12, the transducer converts the electrical energy applied to sonic energy, causing the front end 24 of the horn to vibrate, thus producing radial shock Waves which produce cavitation in the liquid 32. This cavitation reflects itself as a highly efficient scrubbing action against the inside surfaces of the pipe 30, removing soil and other contamination which normally adheres to the inside wall of the pipe. Due to the low impedance of the air trapped within the barrel portion 22, very little sonic energy is dissipated within the barrel of the horn itself, causing most of the energy to be radiated toward the pipe. The transducer is moved along the length of the pipe by manipulating the cable 14. This may be done manually or by a motorized motion mechanism.

Tests have shown that results far superior to other cleaning methods are achieved by this arrangement. Instead of trapping air or another gaseous medium within the barrel, the barrel may be fitted with a low acoustic impedance material, such as foamed cellular cellulose acetate where small bubbles of air are entrapped within plastic material. Although the material in direct contact with the horn will melt due to frictional heat, the center portion will remain useful for a period of time. The use of material other than gas is necessitated when the transducer unit is used in a direction which deviates from the vertical axis and the entrapped gas would normally escape.

Although the mode of operation with a low acoustic impedance medium disposed within the horn barrel is preferred, it should be understood that the present apparatus may be used also without such provision, particularly when horizontal pipes need to be cleaned. In such instances a portion of the acoustic energy will be dissipated within the cavity of the horn, accounting for a somewhat less efficient cleaning arrangement.

It should be noted that the bell-shaped portion of the horn preferably is as large in diameter as is possible, taking into account the parameters involved in acoustic horn design and the mechanical clearance required by pipe joints, couplings, and the like. The horn length is adjusted to constitute a one-half wavelength resonator at the resonant frequency of the transducer unit. For the general theory of designing horns, reference is made to the book Ultrasonic Engineering by Julian R. Frederick, John Wiley & Sons, Inc., New York, NY. (1965) LC. Card 65-14257, page 87 Design of Solid Horns for Piezoelectric and Magnetostriction Transducers.

While there has been described and illustrated a certain preferred embodiment of the present invention and certain further modifications have been indicated, it will be apparent to those skilled in the art that still further and other changes and modifications may be made therein without deviating from the broad principle and intent of this invention, which shall be limited only by the scope of the appended claims.

What is claimed is:

1. A method for cleaning a pipe comprising the steps of:

filling the pipe with a liquid;

immersing in the liquid an electro-acoustic transducer which is provided with a horn having a bell-shaped front portion;

applying alternating electrical energy to activate said transducer to generate sonic energy whereby to cause radial vibrations at said front portion, said vibrations being of sufficient magnitude to cause cavitation in said liquid, and

providing relative longitudinal motion between said transducer and said pipe to clean consecutively different portions of said pipe.

2. A method for cleaning a pipe as set forth in claim 1 whereby the transducer is inserted in the pipe so that the barrel portion of said bell-shaped front portion is occupied at least partially by a medium having a low acoustic impedance.

3. A method for cleaning a pipe as set forth in claim 2 wherein said medium is a gas.

4. A method for cleaning a pipe as set forth in claim 2 whereby said vibrations are produced at a frequency of at least one kilocycle per second.

5. A method for cleaning a pipe as set forth in claim 2 wherein said liquid is a solvent.

6. A method for cleaning a pipe comprising the steps of:

maintaining the pipe in a substantially vertical position;

filling the pipe with a liquid;

immersing in said liquid an electro-acoustic transducer which is provided with a horn having a bell-shaped front portion, such immersing being effected in a manner that air is trapped in the barrel of said bellshaped portion;

applying alternating electrical energy to activate said transducer to generate sonic energy whereby to cause radial vibrations at said front portion, said vibrations being of sufficient magnitude to cause cavitation in said liquid, and

providing relative longitudinal motion between said transducer and said pipe to clean consecutively different portions of said pipe.

7. An apparatus for cleaning a liquid filled pipe with sonic energy comprising:

an electro-acoustic transducer unit immersible in a liquid and provided with a horn having a bell-shaped open ended front portion which is adapted to vibrate in the radial mode, and

means for energizing said transducer with high frequency electrical energy whereby said horn is caused to vibrate and to produce cavitation in the liquid, such ca (itation causing a scrubbing of the inside surface of the pipe.

8. An apparatus for cleaning a liquid filled pipe as set forth in claim 7 wherein the barrel portion of said bellshaped front portion is occupied at least partially by a medium having a relatively low acoustic impedance.

9. An apparatus as set forth in claim 8 wherein said medium having a 10W acoustic impedance is a gas.

10. An apparatus for cleaning a liquid filled pipe as set forth in claim 7 wherein said electrical energy has a frequency of at least one kilocycle per second.

11. An apparatus as set forth in claim 10 wherein said liquid is a solvent, and said transducer is adapted to be moved longitudinally within said pipe.

12. An apparatus for cleaning a liquid filled enclosure with sonic energy comprising:

an electro-acoustic transducer unit immersible in a liquid confined in an enclosure, said transducer unit being provided with a horn having a hollow front portion which is adapted to vibrate in the radial mode;

a source of ultrasonic frequency electric energy;

coupling means between said source and said transducer unit for energizing said transducer unit with electric energy whereby to produce vibrations in said radial mode, said vibrations being of sufiicient intensity to cause cavitation in the liquid, and

means for causing said transducer unit when immersed in the liquid to be movable relative to the enclosure.

13. An apparatus for cleaning a liquid filled enclosure as set forth in claim 12 wherein the front portion of said horn terminates in an annular rim of decreasing cross sectional area.

References Cited UNITED STATES PATENTS 3/1948 Bodine. 2/1962 Welkowitz 134--1 X US. Cl. X.R. 134-17, 167; 3l08 

